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A090368 a(1) = 1; for n>1, smallest divisor > 1 of 2n-1. 17
1, 3, 5, 7, 3, 11, 13, 3, 17, 19, 3, 23, 5, 3, 29, 31, 3, 5, 37, 3, 41, 43, 3, 47, 7, 3, 53, 5, 3, 59, 61, 3, 5, 67, 3, 71, 73, 3, 7, 79, 3, 83, 5, 3, 89, 7, 3, 5, 97, 3, 101, 103, 3, 107, 109, 3, 113, 5, 3, 7, 11, 3, 5, 127, 3, 131, 7, 3, 137, 139, 3, 11, 5, 3, 149, 151, 3, 5, 157, 3, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Remi Eismann, Table of n, a(n) for n = 1..10000

MATHEMATICA

Join[{1}, Divisors[#][[2]]&/@Range[3, 161, 2]] (* Harvey P. Dale, Oct 09 2011 *)

PROG

(PARI) a(n)=if(n>1, factor(2*n-1)[1, 1], 1) \\ Charles R Greathouse IV, Nov 09 2016

CROSSREFS

Bisection of A020639.

Cf. A100773.

Sequence in context: A255562 A130140 A051417 * A120374 A088836 A076565

Adjacent sequences:  A090365 A090366 A090367 * A090369 A090370 A090371

KEYWORD

nonn

AUTHOR

Lekraj Beedassy, Nov 27 2003

EXTENSIONS

More terms from Ray Chandler, Dec 02 2003

Definition corrected by Rémi Eismann, May 08 2007

STATUS

approved

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Last modified May 26 09:12 EDT 2017. Contains 287093 sequences.